Femtocell Fingerprinting

Abstract

User equipment (UE) includes an architecture for handling femtocell fingerprints. The architecture may, as examples, maintain the validity and reliability of fingerprints and coordinate enhancement to existing fingerprints. The architecture also supports fingerprint creation, updating, and deletion.

What is claimed is: 
     
         1 . A method comprising:
 establishing a central fingerprint database operable to store fingerprints for proximity detection, the fingerprints characterizing femtocells;   executing a fingerprint manager in communication with the fingerprint database for:
 creating the fingerprints, and storing, for the fingerprints, fingerprint components that characterize the femtocells; 
 selectively updating the fingerprint components; and 
 deleting selected fingerprints among the fingerprints; and 
   executing a proximity detector in communication with the fingerprint database, and, with the proximity detector:
 obtaining environmental measurements; 
 analyzing the fingerprints to find a matching fingerprint with respect to the environmental measurements; and 
 initiating a cell search for a specific femtocell that corresponds to the matching fingerprint. 
   
     
     
         2 . The method of  claim 1 , further comprising:
 determining a particular femtocell for enhanced fingerprinting, and in response:   creating multiple fingerprints in the central fingerprint database for that particular femtocell.   
     
     
         3 . The method of  claim 2 , where determining comprises:
 determining the particular femtocell responsive to frequency of selection of that particular femtocell.   
     
     
         4 . The method of  claim 2 , where determining comprises:
 determining the particular femtocell responsive to recency of selection of that particular femtocell.   
     
     
         5 . The method of  claim 1 , further comprising:
 obtaining at least some of the fingerprint components from radio resource control measurements of neighboring macrocells.   
     
     
         6 . The method of  claim 1 , further comprising:
 obtaining at least some of the fingerprint components from positioning system measurements of location.   
     
     
         7 . The method of  claim 1 , further comprising:
 obtaining at least some of the fingerprint components from wireless network measurements of visible access points.   
     
     
         8 . The method of  claim 1 , where creating the fingerprints comprises:
 creating multiple different fingerprints corresponding to multiple different physical approaches to a particular femtocell among the femtocells.   
     
     
         9 . The method of  claim 1 , further comprising:
 determining when a particular fingerprint among the fingerprints has triggered more than a threshold number of failed connection attempts, and in response:   deleting that particular fingerprint from the central fingerprint database.   
     
     
         10 . The method of  claim 1 , where creating the fingerprints comprises:
 creating the fingerprints responsive to successful connections to the femtocells.   
     
     
         11 . A system comprising:
 a central fingerprint database operable to store a fingerprint of a femtocell;   a fingerprint manager in communication with the fingerprint database, the fingerprint manager configured to:
 create the fingerprint in the fingerprint database, and store, for the fingerprint, a fingerprint component that represents a characteristic of the femtocell; 
 determine a reliability criteria for the fingerprint; and 
 delete the fingerprint when the reliability criteria fails the reliability threshold; and 
   a proximity detector in communication with the fingerprint database, the proximity detector configured to:
 obtain location information applicable to a device; 
 compare the fingerprint to the location information to determine whether to trigger a cell search; and 
 initiate an attempt to connect the device to the femtocell when the cell search is triggered. 
   
     
     
         12 . The system of  claim 11 , where:
 the reliability threshold comprises a count of connection failures for the femtocell.   
     
     
         13 . The system of  claim 11 , where:
 the proximity detector is further configured to:   increase time between subsequent attempts when a prior attempt has failed.   
     
     
         14 . The system of  claim 11 , where:
 the fingerprint manager is further configured to:   create an additional fingerprint for the femtocell, where the additional fingerprint characterizes a different physical approach to the femtocell.   
     
     
         15 . The system of  claim 11 , where:
 the fingerprint component comprises a macrocell identity for a macrocell visible from the femtocell.   
     
     
         16 . The system of  claim 11 , where:
 the fingerprint manager is further configured to:   update the fingerprint when an update criteria is met.   
     
     
         17 . The system of  claim 16 , where:
 the update criteria comprises an updated frequency configuration of the femtocell, a neighboring cell, or both.   
     
     
         18 . The system of  claim 16 , where:
 the update criteria comprises a changed physical cell identity or a changed primary scrambling code.   
     
     
         19 . A system comprising:
 a non-volatile fingerprint memory;   a central fingerprint database;   a fingerprint manager in communication with the fingerprint database, the fingerprint manager configured to:
 restore, after power-up, a fingerprint of a local cell for a restricted subscriber group from the non-volatile fingerprint memory to the central fingerprint database; 
 create the fingerprint in the fingerprint database, and store, for the fingerprint, fingerprint components comprising characteristics of the local cell; 
 update the fingerprint when an update criteria is met; 
 determine a reliability criteria for the fingerprint; and 
 delete the fingerprint when the reliability criteria fails the reliability threshold; 
   a proximity detector in communication with the fingerprint database, the proximity detector configured to:
 obtain environment characteristics applicable to a device; 
 compare the fingerprint to the environmental characteristics to determine whether to trigger a cell search; and 
 initiate an attempt to connect the device to the local cell when the cell search is triggered; and 
   where the fingerprint manager is operable to obtain the fingerprint components from among:
 a radio resource control input operable to convey a macrocell measurement as a fingerprint component to the fingerprint manager; 
 a positioning system input operable to convey physical location information as a fingerprint component to the fingerprint manager; and 
 a wireless network input operable to convey wireless access point information as a fingerprint component to the fingerprint manager. 
   
     
     
         20 . The system of  claim 19 , where:
 the proximity detector is further operable to:   perform a phased comparison to the fingerprint, including a coarse match that triggers a subsequent acquisition of additional environment characteristics; and   confirm identity of the local cell by acquiring system information.